The antioxidant power of several phenolic acids and related food samples is estimated from the generation and growth of gold nanoparticles. The intensity of the resulting particle plasmon absorption bands correlates well with the redox characteristics of these phenolic acids estimated from cyclic voltammetry experiments. The highest capacity of reducing gold(III) to gold nanoparticles corresponds to the highest antioxidant activity, consistent with the tendency of phenolic acids to donate electrons.

The aim of the present research was to identify principal parameters determining the oxidative stability of microencapsulated fish oil. Microcapsules were prepared by spray-drying using different types of n-octenylsuccinate-derivatized starch, gum Arabic, sugar beet pectin, sodium caseinate, and/or glucose syrup. Two principal components to classify the different microcapsules accounting for up to 79% of the variance were identified. The principal components were determined by physicochemical parameters reflecting the emulsifying ability of the encapsulant and the drying behavior of the parent emulsion. Microcapsules, which were identified by principal component analysis to be significantly different, exhibited a low stability upon storage, showing that the principal components and, thus, the underlying physicochemical parameters analyzed in the present study are correlated with core material stability.